In this paper we present the design and implementation of a computer network to fulfil the needs of a scientific library, making use of Open Source technologies. For a scientific library it is vital to guarantee users to access all the online licensed resources, such as e-journals and e-books, the library subscribes to. However, access through the network and Internet (via a wireless or cable connection) has to comply with the license (for instance: library has to guarantee that users do not perform prohibited activities, such as systematic and programmating downloads, ..) and with the law. In the paper we describe the implemented solutions for authenticating and authorising users, controlling user access and preventing risks or abuses.